AREA NEAR EARLHAM 



693 



subtilita, many crinoid stems, and a few Marginifera muricata. Beneath 

 these heavy beds about 3 feet of a gray shale appear exposed in the side 

 of the trench. Two miles to the northwest of this outcrop are two out- 

 crops of a very fragmental limestone in which no fossils were noted. In 

 the judgment of the writer, these various beds in section 35 and to the 

 northwest are not Hertha and other beds of the Kansas City division of 

 the Missouri stage, as they have previously been mapped. They will be 

 considered later as a portion of the Henrietta (Appanoose) substage of 

 the Des Moines stage. 



Contrasts on the Two Sides of Fault 



The Hertha limestone universally in Iowa and northern Missouri has 

 numerous Composita subtilita in it and occasionally representatives of 

 other forms, but essentially only Composita subtilita. The topmost 

 stratum of the Hertha on the south side of the fault-plane is dense and 

 resistant to weathering. The previously supposed Hertha northwest of 

 the fault contains few fossils, is arenaceous, and yields readily to weather- 

 ing, so that the outcrops present a loose mass of arenaceous lumps. It is 

 not Hertha limestone. 



In the Ladore shale, just above the true Hertha limestone, on the south 

 side of the fault, there is a bed of blue limestone that has coal below it 

 and black shale above it. At the outcrop northwest of Earlbam, beyond 

 the fault, the shale that appears is an ordinary gray shale, with no evi- 

 dence of blue limestone in the bed of the ravine nor along the side of the 

 trench. 



The true Bethany Falls (Earlham) limestone, next above the Ladore 

 shale on the south side of the fault, has at its base a bed of limestone 

 about a foot and a half thick. Above this base are beds of various thick- 

 nesses of limestone up to 6 inches, as may be seen in the old quarries 

 east of Earlham and elsewhere. The beds of. limestone across the fault 

 to the northwest of Earlham are divided into two parts. The basal por- 

 tion, 8 feet thick, is a continuous mass of limestone. The upper portion 

 is scarcely more than calcareous shale. Further, the assemblage of fossils 

 found in the lower portion, even without the Marginifera muricata, which 

 is considered an index fossil of the Des Moines stage, is such as can not 

 be found anywhere in the Bethany Falls (Earlham) limestone of Iowa. 

 The assemblage is marked by exceedingly numerous Reticularia perplexa, 

 with frequent Spnrifer cameratus, Composita subtilita and crinoid stems, 

 and the presence of Marginifera muricata. Such a succession of strata 

 and assemblage of fossils are not to be duplicated either in the Pleasanton 



